House insulation

[Tonyz]

Renovators help please. We have a rental house in Adelaide that about40 years old. When built it had fiberglass batts put in the ceiling and an iron roof.. The roof now needs replacing so what do I do about the batts? Pull out the old ones and replace or just put new ones over top. How much more effective is the foil that goes between the roof frame and the new iron. Remember this is just rental.

Thanks Tony

[DJ’s Timber]

If it's only a rental, I would leave the old batts in place and put foil on with the new tin. The foil does cut down the heat from the sun a fair bit and it's cheap compared to new insulation

[Burnsy]

If the roof needs replacing why are you worrying about the batts? Don't do anything to them, leave them there.

Same goes for the old roofing battens. Put down new roofing battens next to the old ones that meet current standards and tek the roof straight onto them, it will save you time ripping out and paying for disposal of the old ones. If there is a problem with the insulation such as it does not work very efficiently your best bet is to leave the old in place and buy some rolls of aircell to roll out over the old roofing battens before you screw the news ones in place. make sure you overlap the aircell by at least 50mm and tape the entire seam with a quality tape, the reinforced stuff is best (probably why it is $20 a roll).

[rod@plasterbrok]

New batts won't work any better than the old batts.

Unless of course you want to increase the overall effeciency.

[MikeT]

My understanding is that new fibre batts will work better, not just because they're a little more efficient these days but because they tend to become brittle with age and the so the number of cells to trap the air reduce. With mine - with workmen getting up in the roof over the last 30 years I've noticed they're somewhat worse for wear with gaps etc where they haven't bothered to take proper care of them.

Having said this it isn't going to make a heap of difference - particularly since - if the house is that old - there's probably no insulation in the walls. If you want to improve it then laying some foil (or better the aircell stuff) over the top sounds like the go.

Putting sarking under the roof won't actually make the house much warmer in winter (given the roof cavity is adequately ventilated - and it isn't a cathedral ceiling). Sarking, however, will make the house a lot cooler in summer. Without the sarking the roof cavity heats up to stupid temperatures and eventually it will conduct through the batts and into the house over a hot work day when no ones home - the batts then actually prevent the heat getting back out.

Personally, I'd remove the old battens - and lay the sarking underneath. The sarking works more efficently when there's somewhat of an air gap between the roof and the sarking - no conduction can then occur between the tin and the sarking.

The fact that it's a rental shouldn't really make much difference. Having spent plenty of years renting there's nothing more frustrating than landlords that give you short shrift. Not saying you're doing this but keep in mind that people still have to live in the place and if you can make it more comfortable for what is a minimal extra cost then to me it's worth doing for the warm fuzzy feeling alone. With house prices these days there are plenty of people that are going to be in rentals their entire life.